Burners

ABSTRACT

A burner element for fluid fuels provided with a plurality of tubular combustion air passages which extend through a fuel supply gallery, the fuel gallery being provided with a number of fuel outlet passages and a surface member in the form of a sheet of metal material arranged to extend ajacent one end of the combustion air passages, the surface member being provided with a plurality of tubular projections corresponding with the plurality of combustion air passages, the tubular projections being arranged to extend outwardly from the element, of which the following is a specification.

United States Patent [191 Ware Apr. 23, 1974 l BURNERS l,968,395 7/1934Henson 431 353 7, [75] Inventor: Peter G. Ware, Rugby, England 394,545 71905 Phlllips 431 354 s g Dunlop Limited, London, England PrimaryExaminer-Carroll BIDority, Jr.

[22] F June 29 7 Attorney, Agent, or Firm-Stevens, Davis, Miller &

Appl. No.: 267,621

Foreign Application Priority Data July 3, 1971 Great Britain 31272 71 r[52] us. Cl... 431/353, 431/354, 239/4255, 239/557 [51] Int. Cl. F23d13/02 [58] Field of Search 431/353, 354; 239/4245, 239/4255, 557, 424

5 1 1 References Cited UNITED-STATES PATENTS 1,703,684 2 1929Morley...... 239/4245 621,248 3/1899 Heller 1. 239/424 7 6,494 8/1904Crone 239/424 Mosher [5 7] ABSTRACT A burner element for fluid fuelsprovided with a plurality of tubular combustion air passages whichextend through a fuel supply gallery, the fuel gallery being providedwith a number of fuel outlet passages and a surface member in the formof a sheet of metal material arranged to extend ajacentone end of thecombustion air passages, the surface member being provided with aplurality of tubular projections corresponding with the plurality ofcombustion air passages, the tubular projections being arranged toextend outwardly from the element, of which the following is aspecification.

7 Claims, 5 Drawing Figures l PMEMTEBAPR 23 m4 SHEET 3 OF 3 i-EQSOBLBOThot.

BURNERS through a fuel supply gallery so that the emission of fuel intothe combustion zone of the burner element can be arranged to entraincombustion air.

In one such burner element construction of this kind I the fuel supplygallery is formed between two sheet or strip members arranged in asuperimposed spaced relationship. The combustion air passages aredefined by forming corresponding pairs of apertures in the two sheet orstrip members and forming the material surrounding at least one of theapertures of each pair into a tubular projection which is arranged toextend into interfitting relationship with either the other aperture ofthepair or a tubular projection extending from the material surroundingthe other aperture of the pair. Fuel outlet passages are provided in thefuel supply gallery to enable fuel to flow from the gallery into the airflow through the combustion air passages. Burner elements of this kindare described in British Pat. No. 1,325,443 and U. S. Pat. No.3,648,665.

In the operation of burner elements of the kind described in thepreceding paragraph it may be necessary to limit the heat output rate ofthe element to prevent lift off of the flames. The phenomenon of ?liftoff occurs when the velocity of the gas issuing from the element exceedsthe flame velocity of the gas, the base of the flames then rising fromthe surface of the element so that theflame becomes unstable andsubsequently extinguishes itself. a

Alternatively it may be necessary to limit the heat output rate of theburner element in order to prevent the material of the element frombecoming excessively Whether it is the phenomenon of lift off" orexcessive heating of the element which limits the heat output I rate of.the burner element will depend on the type of fuel being used and on theconstructional details of the element. I

One object of the present invention. isto provide an improved burnerelement for use with liquid or gaseous fuel.

According to one aspect of the present invention a burner element forfluid fuels comprises a fuel supply gallery provided with a plurality oftubular combustion air passages extending therethrough, the fuel supplygallery being provided with a number of fuel outlet passages and asurface member in the form of a sheet of metal material arranged toextend adjacent one end of :the combustion air passages, the surfacemember being provided with a plurality of tubular projectionscorresponding with the plurality of combustion air passages, the tubularprojections being arranged to extend outwardly from the element. I a

The surface member may be arranged adjacent the lower or inlet ends ofthe combustion air passages so as to reduce the temperature of theelement .by improving the rate of heat transfer between the element andthe combustion air flowing into thecombustion air passages.Alternatively the surface member may be arranged adjacent the upper oroutlet ends of the combustion air passages so as to improve the flamestability of the element, and raise the heat output rate at which theburner element can operate without the occurrance of lift off. Ifdesired a surface member may be provided adjacent both'ends of thecombustion air passages in orderto' derive the benefits associated withboth these arrangements.

According to another aspect of the present invention a burner elementfor fluid fuels comprises an upper and a lower sheet member arranged inspaced superimposed relationship and sealed around their edges to form afuel supply gallerytherebetween, the members being provided with aplurality of apertures arranged in pairs, each pair comprisingoneaperture in each member and the apertures of each pair beingsuperimposed, at least one member being of sheet metal material and thesheet metal surrounding one aperture of each pair extending as a tubularprojection into association with the material surrounding the otheraperture of the pair thus defining a plurality of combustion airpassages extending through the gallery, the areas of at least one memberaround the said apertures being arranged to permit fuel to pass from thefuel supply gallery, a surface member of sheet metal. material beingarranged adjacent one sheet member, the surface memberbeing providedwith a plurality of tubular projections corresponding with thecombustion air passages and arranged to extend outwardly from theelement.

Four embodiments of the invention will now be described by way ofexample with reference to FIGS. 1. to 4 of the accompanying drawings inwhich: I

FIGS. 1 and 2 show cross-sectional views through burner elements inaccordance with the present invention;

FIG. 3 is a plan view of a circular rosette-shaped burner element inaccordance with the present inventron, I

FIG. 4 is a cross-sectional view on the line X-X of FIG. 3, j I

FIG. 5 is a view similar to FIG. 4 ofa modification of the rosetteshaped burner element. I

In a first embodiment of the invention, shown in FIG. 1, a burnerelement comprises anupper sheet metal member 1 and a lower sheet metalmember 2 which are arranged in spaced superimposed relationship andsealed together around their edges so as to, form a fuel supply gallery3 therebetween. A surface. member 4 is Each combustion air passageisformed by forming a plurality of pairs of apertures in the sheetmembers,

one aperture of each pair being formedin each sheet member, and thenforming the material which surrounds the apertures in the lower sheetmember into tubular projections 8 which extend from the lower membertowards the upper sheet member and into in terfltting association withcorrespondingtubular projections 9 which are of slightly largerdiameter, and

which extend towards the lower sheet member from the material whichsurrounds the apertures in the upper.

sheet member. a

Axially extending grooves 6 are broached or otherwise formed on theradially inner surface of each tubuf lar projection 9 of the upper sheetmember so that when the projections on the upper and lower sheet arebrought into interfitting relationship the grooves form small fueloutlet passages in combination with the projections extending from thelower sheet member. Thus each combustion air passage is provided with anumber of fuel outlet passages spaced around its periphery through whichfuel can flow from the gallery into the air flow through the combustionair passages during operation of the burner.

The surface member 4, which is substantially identical to the uppersheet member except that the tubular projections 12 are formed withoutgrooves, is spotwelded or otherwise secured to the upper sheet member sothat the tubular projections of the surface member correspond with thecombustion air passages and extend outwardly from the burner element.

Suitable techniques for forming the tubular projections in the upper andlower sheet members and the surface member and for forming the groovesin the projections extending from the upper sheet member are describedin the specification of our previously referred to British and US. Pats.

In operation of the burner element, gas or the vapor of liquid fuel,issues from each of the small fuel outlet passages and entrainscombustion air from the associatedcombustion air passage. The fuel andair mixture burns with a diffusion flame in a combustion zone above thesurface member, and the tubular projections of the surface member assistin stabilizing the diffusion flame.

The heat output rate of the kind of burner described above is determinedby the level of pressure existing within thefu'el gallery. The higherthe level of this internal pressure the higher the velocity of the fuelemerging from the fuel outlet passages and the higher the potential heatoutput rate of the burner.

As previously described, with low flame velocity gases, such as naturalgas, lift off occurs when the velocity of the gas issuing from theburner element exceeds the flame velocity of the gas. By arranging thelength of the projections extending from the surface member to delaycombustion until the velocity of the gas emerging has fallen to a levelat which it can burn without lift off a burner element in accordancewith the present invention can be arranged to operate at higher levelsof internal pressure than a comparable burner element not provided witha surface member.

In a second embodiment of the invention, shown in FIG. 2, a burnerelement comprises upper and lower sheet members 1 and 2, substantiallyas described above, arranged in a superimposed spaced relationship toform a fuel supply gallery 3 therebetween and a surface member 10secured in superimposed relationship with the lower sheet member. Thesurface member is provided with tubular projections 11 which extendoutwardly (i.e., downwardly) from the burner element. The surface memberis substantially identical to the lower sheet member, the tubularprojections 11 of the surface member being formed without grooves andbeing of substantially the same diameter as the tubular projections ofthe lower sheet member. A fuel inlet pipe 5 is connected to the galleryas in the preceding embodiment.

In operation of the burner element, gas or the vapor of liquid fuel,issues from each of the small fuel outlet passages 6 and entrainscombustion air, in the manner described in connection with the precedingembodiment, so as to support a diffusion flame in a combustion zoneabove the surface member. The tubular projections of the surface memberassist in conducting heat from the element to the air flowing throughthe combustion air passages and thereby reduce the temperature of theburner element. A further feature of the surface member is that thetubular projections induce turbulence in the flow of air through thecombustion air passages, thereby improving the uniformity of mixingbetween the fuel and air and increasing the flame stability.

Where the burner operates on a high flame velocity gas, such as acomposite gas having a hydrogen content of, for example, 30 per cent ormore, the flame tends to sit on the surface of the upper sheet memberadjacent the combustion zone except when operating at very high internalpressures associated with a heat output rate which is far in excess ofthat which would cause the element to overheat. Therefore, in general,the element attains a higher temperature than when operating on a lowflame velocity gas at a given heat output rate. The provision of asurface member adjacent the lower sheet'member improves the rate atwhich heat is conducted away from the upper sheet member, by reducingthe temperature of the lower sheet member to which heat is conductedfrom the upper sheet member. The surface member is cooled by air flowinginto the combustion air passages, thus cooling the lower sheet member byconduction.

The arrangement described in the preceding paragraph enables the elementto be operated at a higher heat output rate, without causingoverheating, than if no surface member were present.

In a third embodiment of the invention, shown in FIGS. 3 and 4, arosette-shaped burner element comprises a pair of circular sheet metalmembers 1 and 2 which are secured together in spaced superimposedrelationship and sealed around their edges to form a fuel supply gallery3 therebetween in the manner previously described. Combustion airpassages 7 extend through the fuel supply gallery and are each providedwith a plurality of axially extending fuel supply passages 6 of the kindpreviously described. Circular surface members 4 and 10 of sheet metalmaterial, which correspond to the similarly numbered surface memberspreviously described with respect to the two preceding embodiments, aresecured to the upper and the lower sheet members, and a fuel inlet pipe5 is attached to the periphery of the fuel supply gallery.

The four circular sheet metal members are each provided with one centraltubular projection and six peripheral tubular projections disposedsymmetrically in a circular arrangement relative to the centralprojection.

Each surface member is secured to a sheet member of the fuel supplygallery by spot welds or other suitable means and the projections ofeach surface member are of the same diameter as the projections of theadjacent sheet member.

In operation of the burner element, gas or the vapor of liquid fuel,issues from each of the small fuel outlet passages and entrainscombustion air, in the manner described in connection with the firstembodiment, so as to support a diffusion flame in a combustion zoneabove the surface member. The tubular projections of the upper surfacemember assist in stabilizing the diffut and the tubular projections ofthe lower surface member have the effects, as described in respect ofthe sec ond embodiment of the invention, of reducing the temperature ofthe burner element and of inducing turbulence in the air flow so as toimprove mixing of the fuel and the air.

A rosette-type burner element of the kind described is capable ofproviding a high heat output rate compared with known burner elements ofan equivalent surface area, and is particularly suitable for use asamodular type unit. Thus, several burner elements of .this kind may becombined readily by, for example,

connecting each to a common gas supply so as to form a composite elementcapable of giving a range of desired heat output rates. lf desired,]thetubular projections 9 of the upper sheet 1 in FIGS. 3 and 4 can bereplaced by reticulated ,foam metal material 20 illustrated in FIG. 5.Reticuvapor of a liquid fuel.

Although in various constructions described above both the sheet membersdefining the fuel supply gallery are formed from sheet metal, if desiredthe upper sheet member can be formed wholly or in part from porous foammetal material. Similarly the grooves which form the fuel outletpassages in the constructions described .above can be replaced by anannulus of porous foam metal material surrounding the combustion airpassages and through which fuel can flow from the fuel supply gallery.Examples of burner elements which utilize an upper sheet member formedfrom foam metal and foam metal annulii surrounding the combustion airpassages are described in the specification of our previously referredto British and US. Patents.

Similarly, although in the constructions described above the tubularprojections of the surface members have been described as a being of thesame crosssectional shape and substantially the same size as the tubularprojections of the respective adjacent sheet member, this is notessential and numerous variations in the cross-sectional shapes andrelative sizes of the projections on the surface members and theirrespective associated sheet member can be used without departing fromtheprinciples of the present invention.

Having now described my invention what I claim l. A burner element forfluid fuels comprising a fuel supply gallery provided with a pluralityof tubular combustion air passages extending therethrough, the fuelsupply gallery being provided with a number of fuel outlet passagesintermediate the ends of each combustion air passage anda surfacememberin the form of a sheet of metal material contiguous with the fuel supplygallery, thesurface member being provided with a plurality of tubularprojections corresponding with the plurality of combustion air passages,each tubular projection being arrangedto extend outwardly from theburner element in alignment with one of said combustion air passages.

2. A burner element for fluid fuels comprising an upper and a lowersheet member arranged in spaced superimposed relationship and sealedaround their edges to form a fuel supply gallery therebetween, the

members being provided with a plurality of apertures arranged in pairs,each pair comprising one aperture in each member and the apertures ofeach pair being superimposed, at least one member being of sheet metalmaterial and including sheet metal surrounding one aperture of each pairextendingas a tubular projection into association with materialsurrounding the other aperture of the pair thus defining a plurality ofcombustion air passages extending through the gallery, the areas of atleast one member around the said apertures being arranged to permit fuelto pass from the fuel supply gallery into said air passages, a surfacemember of sheet metal material being contiguous with the fuel supplygallery, the surface member being provided with a plurality of tubularprojections each arranged to extend from one aperture of a respectivepair outwardly from the elementas an extension of the combustion airpassage defined by said pair.

3. A burner element according to claim 2 wherein the areas around eachaperture in the upper sheet member comprise annular inserts of porousfoam metal through which the fuel is permitted to pass from thefuelsupply gallery.

, 4. A burner element according to claim 2 wherein the surface member iscontiguous with the upper sheet member. I

5. Aburner element according to claim 2 wherein the surface member iscontiguous with the lower sheet member.

6. A burner element according to claim 2 provided I spaced, superimposedrelationship and sealed around the edges to form a fuel supply gallerytherebetween,

the members being provided with a plurality of apertures arranged inpairs, each pair comprising one aperture in each member and theapertures of each pair being superimposed and sheet metal surroundingeach aperture extending as a tubular projection into interfittingrelationship with a tubular projection surrounding the aperture pairedtherewith, one of each pair of interfitting projections being providedwith a number of axially extending slots circumferentially spaced aroundsaid projections and co-operating with the other projection of said pairto form a number of fuel outlet passages circumferentially spaced aroundeach combustion air passage, and a surface member of sheet metal securedin contiguous relationship to one of the gallery forming sheet metalmembers and having a number of apertures correspondiing to those of saidgalleryelement.

1. A burner element for fluid fuels comprising a fuel supply galleryprovided with a plurality of tubular combustion air passages extendingtherethrough, the fuel supply gallery being provided with a number offuel outlet passages intermediate the ends of each combustion airpassage and a surface member in the form of a sheet of metal materialcontiguous with the fuel supply gallery, the surface member beingprovided with a plurality of tubular projections corresponding with theplurality of combustion air passages, each tubular projection beingarranged to extend outwardly from the burner element in alignment withone of said combustion air passages.
 2. A burner element for fluid fuelscomprising an upper and a lower sheet member arranged in spacedsuperimposed relationship and sealed around their edges to form a fuelsupply gallery therebetween, the members being provided with a pluralityof apertures arranged in pairs, each pair comprising one aperture ineach member and the apertures of each pair being superimposed, at leastone member being of sheet metal material and including sheet metalsurrounding one aperture of each pair extending as a tubular projectioninto association with material surrounding the other aperture of thepair thus defining a plurality of combustion air passages extendingthrough the gallery, the areas of at least one member around the saidapertures being arranged to permit fuel to pass from the fuel supplygallery into said air passages, a surface member of sheet metal materialbeing contiguous with the fuel supply gallery, the surface member beingprovided with a plurality of tubular projections each arranged to extendfrom one aperture of a respective pair outwardly from the element as anextension of the combustion air passage defined by said pair.
 3. Aburner element according to claim 2 wherein the areas around eachaperture in the upper sheet member comprise annular inserts of porousfoam metal through which the fuel is permitted to pass from the fuelsupply gallery.
 4. A burner element according to claim 2 wherein thesurface member is contiguous with the upper sheet member.
 5. A burnerelement according to claim 2 wherein the surface member is contiguouswith the lower sheet member.
 6. A burner element according to claim 2provided with two surface members, one surface member being contiguouswith the upper sheet member and the other surface member beingcontiguous with the lower sheet member.
 7. A burner element for fluidfuels comprising an upper and a lower sheet metal member arranged inspaced, superimposed relationship and sealed around the edges to form afuel supPly gallery therebetween, the members being provided with aplurality of apertures arranged in pairs, each pair comprising oneaperture in each member and the apertures of each pair beingsuperimposed and sheet metal surrounding each aperture extending as atubular projection into interfitting relationship with a tubularprojection surrounding the aperture paired therewith, one of each pairof interfitting projections being provided with a number of axiallyextending slots circumferentially spaced around said projections andco-operating with the other projection of said pair to form a number offuel outlet passages circumferentially spaced around each combustion airpassage, and a surface member of sheet metal secured in contiguousrelationship to one of the gallery-forming sheet metal members andhaving a number of apertures correspondiing to those of saidgallery-forming member, each said aperture of the surface member beingsurrounded by a tubular projection aligned with a respective combustionair passage and extending from the gallery outwardly from the burnerelement.